Signal Detection and Damage Prevention for microprocessor

[tonyctsiu]

Dear All,

I am developing an electronic device with a microprocessor which needs to detect pulses from a strobe. The signal detection is done by an inductor which is put near to the strobe device.

The signal obtained from the inductor ranges from +-1V to +-5V(AC). Duration is very short, it is just about 1 us. I presume the current is very low for those signal. I need to detect the pulse by an IO pin of the microprocessor. All 1V or 5V(AC) signal needs to be converted into logic 1 for the processor.

The processor is CC2510 by TI. It says it can operate from 3V down to 2v. The absolute max voltage for the IO pins are Vdd+0.3V. Does that means if strobe signal are fed to the IO Pin (even when the voltage is about 3v) while the processor is powered off, it might damage processor.

Is there any way to detect the signal properly considering the wide range of voltage from the inductor? Also is there any way to limit the voltage to the IO pins so that there is at most VDD to be applied to the IO pin even the voltage detected is higher. Also when the device is powered down, is there any way to protect the IO PIN?


Thank you in advance,

Tony Chun Tung Siu

 

[erikl]

If you operate the processor on 2V supply, even the ±1V input signal should trigger.
Use the standard input protection circuit between your sensor and the processor input:
R1=1..10kΩ ; use Schottky or Germanium diodes for VDD+0.3V / GND-0.3V protection.